Conventionally, a map information processing apparatus has been known which updates, when traveling a place whose roads are not recorded in its own map information, its map information by detecting the traveling route from its traveling record and by adding it to the map information as a new road. If such a map information processing apparatus adds a new road having a positioning error to the existing map information, a user will suffer a great disadvantage because a result of a subsequent route search will differ from an actually travelable route.
Accordingly, Patent Document 1, for example, discloses a car navigation system that makes a decision as to whether a new road is to be added to the existing map information or not using receiving conditions of a GPS (Global Positioning System). If the present location detected by a position detecting means is not present on any road indicated by the map information stored in the initial recording area of a navigation recording medium, the car navigation system carries out the processing repeatedly that acquires the present location and writes it to an additional recording area of the recording medium. During the processing, the car navigation system estimates the GPS receiving conditions, that is, the positioning error contained in the new road information, from the number of GPS satellites from which the GPS signals can be received. Then, it adds the new road information to the existing map information only when the estimated error is smaller than a prescribed value. The configuration can prevent generating and recording new road information from the GPS signals in poor receiving conditions, and thus prevent the new road information having the positioning error from being added to the existing map information.
Patent Document 1: Japanese patent application laid-open No. 2002-48559.
The technique described in the foregoing Patent Document 1, however, has the following problem. Specifically, the positioning error can actually exist in spite of good GPS receiving conditions, and particularly urban areas have a problem of the so-called multipath problem caused by that surrounding buildings reflect the signals from the GPS satellites. Accordingly, even if the number of GPS signals received from the GPS satellites is enough, the positioning error can sometimes be very large. Thus, the technique, which estimates the positioning error of the new road from the GPS receiving conditions and employs the estimation result as a reference for deciding whether to register the new road as an additional record, presents a problem of exerting adverse effect on the existing functions such as the navigation functions.
The present invention is implemented to solve the foregoing problem. Therefore it is an object of the present invention to provide a map information processing apparatus capable of circumventing the adverse effect on the existing functions by registering only after an appropriate decision as to whether to make additional registration of the new road to the existing map information.